Feb 2, 2013 3:38 PM

I found this fossil on Robin hoods bay in Yorkshire a few years ago and was wondering what it is. I assume it is some sort of ammonite but im not 100% sure. Any help identifiying it would be greatly appreciated, thank you.

Yes, I agree! Gryphaea Lamark, a bivalve. Upper Triassic - Jurassic sediments (mostly found in the Jurassic). They 'reclined' on the sediment (often mud).

I have been trying to get this to species level, but we do not have a photograph of the smaller valve. and there is no scale bar. According to the rocks in your area, it is likely to be Gryphae mccullochi SOWERBY, however, I will let you decide for yourself by looking at the images and comparing them with your specimen with those on page 9, Figure 1.13, at: http://jncc.defra.gov.uk/pdf/V30chap1_p2.pdf (British Lower Jurassic stratigraphy: an introduction).

Please post your decision and the photograph of the other side as your evidence. I look forward to hearing the verdict!

FYI "An iconic fossil for an icon of palaeontology. Mary Anning (1799-1847), now one of the most celebrated pioneers of palaeontology, is usually associated with her famous discoveries of marine reptiles such as Ichthyosaurs and Plesiosaurus and the pterosaur Dimorphodon.

Gryphaea obliquata, along with Gryphaea arcuata, are commonly referred to as Devil’s toenails and are both found in the Lower Lias (Lower Jurassic) of Britain. They may not be the most obvious choice to associate with Mary, but as one of the most distinctive and abundant fossils of the Lower Lias, Gryphaea was as familiar to her as it is to fossil collectors that scour the beaches at Lyme Regis today."

I hope this is of interest to you - apologies if I have gone into too much detail - but I found your fossil find interesting.

Thank you for all of your help everything you have said has been really interesting and definitely not too much detail. It seems that the indentation seen in most Gryphaea has been filled in on my specimen but judging by the size I would say it is Gryphaeaarcuata. I have included pictures from different angles as evidence. Once again thankyou.